Large magnetocaloric effect in La-based manganite composites near room temperature

The refrigerant materials to be used in magnetic cooling systems must have large RCP values near room temperature as well as large magnetic entropy changes. In order to achieve this, in this study, composite materials were formed to overlap the magnetic entropy maximums of La0.67Ca0.27Sr0.06MnO3 (LCSM) and La0.7Sr0.3Mn0.94N0.06O3 (LSMN) manganite which exhibit second order magnetic transition just below and above room temperature, respectively. The structural, magnetic and magnetocaloric properties of composite materials were investigated. The -Delta S-M(max) values of LCSM and LSMN manganite are determined as 7.12 and 3.90 Jkg(-1) K-1 under 5 T magnetic fields, respectively. By obtaining the composite form of these two manganites, which shows magnetocaloric properties at temperatures close to room temperature, larger RCP values, which are of great technological importance, were obtained in a wider operating temperature range by bringing these two entropy peaks closer to each other. It is seen that the transition temperature in composite compounds shifts to the transition temperature region of whichever manganites forming the composite is dominant. RCP value was calculated as 317.70 Jkg(-1) at 5 T for the 0.75 LCSM/0.25 LSMN composite.